Compressor wash systems pertain to cleaning a compressor air flow path. Due to the combination of large mass flow, dimensionally large inlet, large blades susceptible to erosion, and/or high compression ratios, cleaning the compressor while in operation has many difficulties.
In particular in gas turbine applications, large mass flow requires a large fluid or fluid flow for proper cleaning, which can cause flame out on combustion systems, such as a low NOx PPM combustion system. A large inlet requires multiple and possibly many water injection points to properly cover the rotating and non-rotation blades. Cleaning of the particles off the blades while balancing the effects of erosion may require a wide range of fluid droplet sizes for systematically different amounts of time. A high compression ratio evaporates the water, making cleaning later stages not possible, thus placing more emphasis on cleaning the prior stages. Moreover, installations in the field demand an easily repeatable procedure, and, as many interference issues may exist, a rugged yet compact design is required.
High concentrations of a fluid, such as but not limited to water, aid in cleaning effectiveness. However, due to combustion instability that high concentrations of a fluid, such as water, may cause, there is a limit to the amount of a fluid that can be injected into the compressor. To mitigate the issue of high concentrations of a fluid and flame out, multi-staging of the fluid injection points or nozzles may allow for cycling the nozzles for locally higher concentrations of fluid to air to be impinged on the stationary and rotating blades of the compressor for increased or maximum cleaning efficiency.
Industrial stationary compressor inlets may, for example, include an inlet filter housing, inlet cone, bellmouth casing, and inlet struts. The compressor may be used in various applications, including providing compressed air to industrial large frame gas turbines, and may also be used in the oil and gas industry for natural gas compressor applications, commercial power generation, such as oil and gas platforms, boats, or any other application in which compressors may be useful. Nozzle placement for compressor cleaning may be subject to consideration for the particular application, such as, for example, various mass flow rates that affect the fluid water to air ratio and trajectory of the water flow.
At base load, the air inlet velocity may differ greatly by around 10 times at the first stages radially along the blades from compressor blade root to tip, with the lowest velocity near the blade root. Fluid, such as water, not injected directly in the high velocity areas have proven to be directed towards the blade root, resulting in concentrated erosion of the highest stressed part of the blade. Properly cleaning the blade tips for online washing requires line of sight, from nozzle injection point to blade tip, as well as being located in the high velocity region.
Large water droplets may typically have a much larger impact than smaller droplets on the blades, which aid in a higher leading edge erosion rate. The blade root is the highest stressed part of the blade, and leading edge erosion may be a problem. Keeping the area clean and erosion to a minimum requires the use of small droplets. Shorter blasts of large droplets typically aid in cleaning effectiveness but should be used sparingly if used at all.
For example, in a compressor wash system that includes a multi-stage manifold, opening all stages at once may reduce the manifold back pressure and thus increase the fluid droplet size. Fluctuating fluid droplet size between large and small may aid in cleaning effectiveness in two ways: (1) large droplets may reach further stages of the compressor as they may take longer time to evaporate as they travel downstream the compressor, and (2) for a consistent compressor mass flowrate, varying pressure and fluid droplet size may change the impact region of the water droplets.
Designing an effective online wash with adequate compressor intake throat coverage may require nozzle installations in a geometrically difficult area due to casting thickness, curvature, access, and interferences, while maintaining a rugged design capable of withstanding an industrial environment.
Thus, an effective and efficient compressor wash system that addresses these needs and constraints, as well as others, is desired.